Radar scanning system



Patented May 11, 1954 RADAR SCANNING SYSTEM Henry J. Riblet, WellesleyHills, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass.,a corporation of Delaware Application September 30, 1950, Serial No.187,803

9 Claims. 1

This invention relates to radar scanning systems and more particularlyto scanning systems using hollow rigid wave guides.

Where hollow rigid wave guides are used proper scanning becomes animportant problem, particularly where movement of the horn or radiatingelement is required. Structural complica tions arise in achieving suchfreedom of movement without impairing the energy guiding characteristicsof the wave guide. Because of these structural difficulties, the use ofvarious joints have been generally resorted to. However, such jointspresent difiicult problems in obtaining a suitable degree of scanningfreedom. Pursuant to the present invention, freedom in scanning isachieved in rigid wave guide structures by providing a suitable Waveguide radiator, such as a horn, as an independent unit movable withrespect to the wave guide and coupling the horn by means of a probe tothe wave guide so as to transmit the energy from the wave guide to thehorn for directive radiation, and by inserting in the path of theradiated energy a fixed beamshaping element, such as a lens or parabolicrefiector. Movement of the horn with respect to the beam-shaping elementthereby causes scanning of the shaped beam in a direction correspondingto the movement of the horn. By making the horn integral with a shortwave guide segment arranged parallel to the wave guide, both mechanicalstructural arrangements for moving the horn and energy transfer couplingare greatly facilitated. In such case, the segment may be made to slidein guides fixed to the Wave guide and may be suitably moved by a rack,pinion and motor arrangement. Energy transfer coupling may be achievedby providing a probe extending from the internal cavity of the Waveguide, preferably in the direction parallel to the electric field,through an elongated slot in the side of the wave guide and throughholes in opposite sides of the segment terminating in an adjustableplunger in a short-circuited stub on one side of the wave guide segment.The structure also preferably incorporates a reflecting loop in thecavity of the wave guide and terminating in a base portion in electricalcontact with the segment, the loop being positioned with respect to thecoupling probe in a manner to provide maximum transfer of energy throughthe probe to the segment. To minimize spurious reflections the waveguide may be terminated in an absorbent load, such as suitably bondediron particles. The segment may also be terminated by an adjustableplunger positioned with respect to the probe for optimum operatingcharacteristics. By providing a reflecting surface, such as a plate orscreen for directing toward the beam-shaping element, the energyradiating from the horn and providing for angular rotation of thereflecting surface about an axis parallel to the direction of movementof the horn, scanning in a direction perpendicular to the horn is alsoachieved. Angular rotation of the reflecting surface may be obtained bya suitable pivotal structure, as a rotational axis with movementcontrolled by a gear, pinion and motor arrangement.

These and other features, advantages and objects of the invention willbecome more apparent from the following description taken in connectionwith the accompanying drawings illustrating an embodiment of theinvention, wherein:

Fig. 1 is a schematic plan view of the embodiment of the invention withthe Wave guide and wave guide segment shown in cross section on line Iof Fig. 2; and

Fig. 2 is a front elevation of the embodiment in Fig. 1 wherein only aportion of the wave guide is shown.

Referring to Figs. 1 and 2 in more detail, a portion of a wave guide l0,which is severed from the rest of the wave guide at the line l2 and ofconventional rectangular rigid construction, has propagated therein inthe direction of arrow l4 microwave radio energy from a suitable source,such as a magnetron (not shown). The end [6 of the wave guide [0 ispreferably sealed with an energy absorbent load l8, which may consist ofsuitable bonded iron particles or the like. The wave guide I0 isprovided at its side 20 with a long, narrow slot 22 preferablydimensioned and positioned for minimum loss of energy and through whichprojects an energy reflecting loop 24 and a coupling probe 26. Thereflecting loop 24 may be of conventional design shaped for resonance atthe frequency in the wave guide with its base 28 in electrical contactwith side 30 of a wave guide segment 32, as by silver soldering of base28 to side 30. The reflecting loop 24 is positioned with respect toprobe 26 so as to cause maximum energy transfer from the wave guide [0through the coupling probe 26 to the Wave guide segment 32. The couplingprobe 26 extends through holes 34 and 36 in the opposite sides of theWave guide segment 32 and terminates in a movable plug 38 in a short-circuited stub 40. The plug 38 is adjusted for a cavity 42 in the stub 40for proper reactance matching of the coupling elements. A movableplunger 44 may also be provided at one end of the wave guide segment 32for impedance matching. The other end of the wave guide segment 32 haspreferably a right angle bend therein which terminates in a horn 46. Thewave guide segment 32 with its horn 46 is mounted to move in a directionparallel to the wave guide ID. A suitable mounting arrangement for thispurpose may consist of guide brackets 48 attached at one side to theopposite sides of wave guide Ill, as by brazing, and guide runners 56and 5| between which are ball bearings 52 confined by a retainer 54. Theguide runners 50 are fixed to guide brackets 48, and guide runners 5!are fixed to segment 32. A suitable rack 58 fixed to one side of thewave guide segment 32 has engaged therein a pinion 60 operated from aconventional reducing gear mechanism 62 powered from an electric motor64 connected to a suitable control element and potential source (notshown) by lines 66.

The horn 46 is directed toward a radio energy reflecting surface 68,such as a plate or screen, which is mounted for angular movement aboutpivots mounted at either end of the reflecting surface 68, as by screwsand brackets 12 and 14, respectively. The pivots 10 are rotatablyarranged in a yoke member 16 fixed as by screws 18 at a base portion 88to a rigid surface, such as a wall 82. Angular rotation of reflectingsurface 68 about the pivot 18 is effected through a gear segment 84fixed to the back side of the reflecting surface 68 and having the pivot18 as an axis. Gear segment 84 is driven by a pinion 86 operated througha reducing gear mechanism 88 by electric motor 90 controlled throughlines 92 leading to a suitable control and power source (not shown). Theangle of the reflecting surface 68 is such that radio energy radiationfrom the horn 46 will be reflected by the reflecting surface 68 througha beam-shaping element, such as lens 94.

In operation, radio energy in the wave guide H1 is picked up by thecoupling proble 26 and propagated in the wave guide segment 32. From thewave guide segment 32 the propagated radio energy is radiated from thehorn 46 toward the reflecting surface 68 from whence it is reflectedthrough the lens 94. Scanning in the plane of the paper in Fig. 1 isobtained by rotation of the reflecting surface 68. Thus when thereflecting surface 68 is in the position shown in Fig. 1, the generaltravel of the radio energy will be perpendicular to the lens 94, makingthe horn 46 appear as an image source 96 behind the reflecting surface68 in line with the direction 98 of reflected rays through the lens 94.If, for example, the reflecting surface 68 is rotated in a clockwisedirection to the position shown by dotted lines I08, the reflected rayswill be in a direction shown by line I02 and the horn will appear as animage from an imaginary source at I04. Thus it is seen that, as thereflecting surface 68 is rotated in one or the other direction, itresults in an apparent movement of the horn or radiation source. Thisapparent movement of the horn or radiation source thereby causes acorresponding movement of the shaped beam emanating from the lens 94 andresults in scanning in accordance with this movement in the plane of thepaper in Fig. 1.

For scanning in a plane perpendicular to that just described with regardto Fig. 1, or in the plane of the paper shown in Fig. 2, the horn,itself, is moved along with segment 32 by means of the rack 58, pinion60, reducing gear 62, and

motor 64. Thus three dimensional scanning is achieved.

This invention is not limited to the particular details of constructionherein described, since equivalents will suggest themselves to thoseskilled in the art. It is accordingly desired that the appended claimsbe given a broad interpretation commensurate with the scope of theinvention within the art.

What is claimed is:

1. A scanning system comprising a rectangular hollow rigid wave guide, awave guide segment disposed to move in parallel relation to said waveguide, a slot in one side of said wave guide, microwave energy couplingmeans extending from said segment through said slot into said waveguide, a horn at one end of said segment for radiating microwave energy,beam-shaping means, and a movable reflecting means disposed to directsaid radiated energy at said beam-shaping means.

2. A scanning system comprising a rectangular hollow rigid wave guide, awave guide segment disposed to move in parallel relation to said waveguide, a slot in one side of said wave guide, microwave energy couplingmeans extending from said segment at said slot into said wave guide, ahorn at one end of said segment for radiating microwave energy, fixedbeam-shaping means, and an angularly movable reflecting means disposedto direct said radiated energy at said beam-shaping means.

3. A scanning system comprising a rectangular hollow rigid wave guide, awave guide segment disposed to move in parallel relation to said waveguide, a slot in one side of said wave guide, microwave energy couplingmeans extending from said segment through said slot into said waveguide, a horn at one end of said segment for radiating microwave energy,beam-shaping means, a reflecting means disposed to direct said radiatedenergy at said beam-shaping means, and means for angular rotation ofsaid reflecting means, the axis of said rotation being substantiallyparallel to the direction of motion of said wave guide segment.

4. A scanning system comprising a source of energy, a radiating horncoupled to said source of energy and disposed to move along a firstpath, a beam-shaping means, and an angularly movable energy reflectingmeans positioned to direct energy radiated from said horn at saidbeam-shaping means along a second path perpendicular to said first path.

5. A scanning system comprising a wave guide, a radiating horn coupledto said wave guide and disposed to move in parallel relation thereto, abeam-shaping means, and an angularly movable energy reflecting meanspositioned to direct energy radiated from said horn at said beam-shapmgmeans.

6. A scanning system comprising a source of energy, an electromagnetichorn coupled to said source of energy and adapted to be moved along afirst path, a reflector positioned to intercept microwave energyradiated from said horn, means for rotating said reflector about an axisparallel to said first path, a beam-shaping element, said reflectorbeing disposed to direct said intercepted energy at said beam-shapingelement along a second path perpendicular to said first path.

7. A scanning system comprising a wave guide, an electromagnetic horncoupled to said wave guide and adapted to be moved along thelongitudinal axis thereof, a reflector ositioned to intercept microwaveenergy radiated from said horn, means for rotating said reflector aboutan axis parallel to said first path, a beam-shaping element, saidreflecting means being disposed to direct said intercepted energy atsaid beam-shaping element.

8. A scanning system for scanning in two directions perpendicular toeach other comprising a Wave guide for transmission of energy along thelongitudinal axis thereof, a horn coupled to said wave guide and capableof radiatin a portion of said energy, a beam-shapin element, areflecting means disposed to direct energy radiated from said horntoward said beam-shaping means, means for moving said horn along saidwave guide parallel to the longitudinal axis thereof for effecting thescanning of said shaped beam in a direction corresponding to themovement of said horn, means for producing angular rotation of saidreflecting means about an axis parallel to the direction of movement ofsaid horn for effecting scanning of said shaped beam in a directionperpendicular to said direction of movement of said horn.

9. A scanning system for scanning in two directions perpendicular toeach other at different rates comprising a wave guide for transmissionof energy along the longitudinal axis thereof, a horn coupled to saidwave guide and capable of radiating a portion of said energy, abeam-shaping element, a reflecting means disposed to direct energyradiated from said horn toward said beam-shaping means, means for movingsaid horn at a first rate alon said wave guide parallel to thelongitudinal axis thereof for effecting the scanning of said shaped beamat said first rate in a direction correspondin to the movement of saidhorn, means for producing angular rotation of said reflecting means at asecond rate about an axis parallel to the direction of movement of saidhorn for effecting scanning at said second rate in a directionperpendicular to said direction of said movement of said horn.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,931,980 Clavier Oct. 24, 1933 2,032,588 Miller Mar. 3, 19362,409,183 Beck Oct. 15, 1946 2,434,253 Beck Jan. 13, 1948 2,452,349Becker Oct. 26, 1948 2,524,292 Iams et a1. Oct. 3, 1950 2,530,580Lindenblad Nov. 21, 1950 2,531,454 Marshall Nov. 28, 1950 2,514,617Albersheim July 11, 1950 2,541,324 Baxter et al. Feb. 13, 1951 2,603,749Kock July 15, 1952

